App lounge: Fetch and display author name from F-Droid, instead of displaying "unknown"

Description

Previously almost all F-Droid apps showed "unknown" as author name.
Now App Lounge can fetch data from F-Droid Gitlab and display the correct author name.
In some cases, if the author name is not present in F-Droid data as well, then display F-Droid as author.

Issue(s)

e/backlog#4427 (closed)

Test environment

Gradle build against 4427-fdroid_unknown_apps branch, install the apk into the device

Test procedures

1. Install the app.
2. Go to Settings.
3. Click Show only open source apps
4. Click Search button.
5. Search for nextcloud.

Author names shown will be either "F-Droid" or actual author names.

Technical details

Screenshots

Check list

• Self review
• Test procedure explained
• Tested on fresh install
• Tested applied as an update
• License
• Internal documentation
• User documentation